Safety Moment #7: Dangers of High Pressure Gas

High pressure gas pipeline pigging incident

We have prepared a set of Safety Moments that can be used in meetings and presentations. Some of them are to do with the process industries, both onshore and offshore, and others are more to do with events in everyday life. We use these Safety Moments to provide insights and thoughts to do with the management of risk and safety at energy and process facilities. This one is to do with the dangers of high pressure gas.

This particular YouTube video discusses some of the hazards associated with the use of high pressure gas. It is illustrated with a serious incident that occurred when a company was trying to clear a line that was blocked with a stuck pig. Fortunately no one was hurt but it was a significant near miss.The storyboard for the video is available here.

The Incident

A contractor was dewatering a 10 mile section after a hydrostatic test. He was using a foam pig

that was pushed along by compressed air to displace the water. The water was being removed from a 12" bypass line. The pig got stuck somewhere in the line so they increased the pressure on the upstream side of the pig to 400 psig (28 barg). Downstream of the restriction the line was open, as shown. The differential force on the pig was almost 0.5 million pounds (2,200 kilonewtons). With that kind of force behind it the pig was going to move.

Dangers of high pressure gas illustrated with pigging incident

In order to catch the pig, a large front end loader was placed in front of the open pipe. The pig shot out of the pipe, flipped the loader and continued to fly approximately 150 meters in the air, destroying a wooden platform along the way.

Fortunately, all personnel had been removed from the area so there were no injuries or fatalities.

Plant Design and Operations

​Book: Plant Design and Operations Our book Plant Design and Operations, and the associated ScienceDirect ebooks, provides guidance to do with the control of high pressure gases, line blinding and pressure tests, both strength and leak tests.